The only preprinted brand I’ve used is Eduard and never had any paint chipping away while bending.

Perhaps applying some varnish before bending might prevent it, with obvious careful manipulation of the PE

You might try the method of placing the prepainted parts in a toaster oven at 400 degrees F for 15-20 minutes. Try it on an unneeded item to see how the paint is affected before using it on your belts.

It always worked well on the PE I used doing WWI aircraft.

Hope this helps,
Paul H

Joel,
I usually did the entire sheet or two at the same time and just removed the parts that I needed to keep in the hardened form so it was not a great deal of wasted energy.

Another method would be to place the painted part in a metal box or tin (i.e. Altoids tin) of some kind and try heating the box over a candle or spirit flame. This could possibly provide flame isolation while still conducting enough heat to anneal the part in relatively short order.

I think it would be worth a try.

Cheers
Paul H